Signal Transmission Apparatus

ABSTRACT

A signal transmission apparatus is connected to a network as one node among a plurality of nodes involved in the network which is provided with an audio signal transmission period for transmitting a plurality of channels of audio signals each transmission cycle and a control data transmission period for transmitting control data of the plurality of the nodes each control cycle by using an idle time period other than the audio signal transmission period. In the signal transmission apparatus, a storage section stores configuration information of the one node. A transmitting section transmits the control data including an error checking code of the configuration information. A receiving section receives request data from another node, the request data requesting the one node for transmission of an information block of the configuration information. A control section controls the transmitting section to transmit the information block in response to the request data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.10/850,613, filed May 19, 2004, the entire disclosure of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a signal transmission apparatus adaptedfor use in a system for transmitting an audio signal through a networkwhile controlling audio amplifiers, mixers and other audio equipmentconnected to the network.

2. Prior Art

In a sound system used at a big concert hall and the like, multiplechannels of audio signals generated by a mixing system and the like aresounded from many loudspeakers through many amplifiers. Since the numberof cables will become enormous if a cable for audio signal transmissionis installed for each individual channel, it is desirable to convertmultiple channels of audio signals into audio data packets and totransmit them through a digital network.

The technology of CobraNet (trademark) is known as a protocol method oftransmitting multiple channels of audio data in real time through anetwork of a CSMA/CD (Carrier Sense Multiple Access with CollisionDetection) system such as the Ethernet (registered trademark). CobraNettechnology is disclosed in Non-patent literature, Audio Networks AnOverview, Cirrus Logic, Inc., 2001.1. In the CSMA/CD system, anarbitration is used when a collision occurs, that is, when two or morenodes start transmission simultaneously. However, the occurrence of acollision actually causes band losses due to arbitration. In view ofthis, CobraNet assigns a transmission period of audio data to each nodeinvolved in the network within one transmission cycle to avoid acollision, thus enabling efficient transmission of up to 128 channels ofaudio data.

Referring now to FIG. 3( a), a general outline of the protocol ofCobraNet will be described. First, in the protocol of CobraNet, audiodata is outputted from each node on the network within one transmissioncycle (denoted 200 in the figure) set at an interval of 1.33 msec. Then,one of nodes is set as a special node (called the “conductor”) formanaging the transmission cycle 200. At the beginning of eachtransmission cycle 200, the conductor outputs a beat packet (startuppacket) 201 on a network 1000.

The output of this beat packet 201 stimulates all nodes including theconductor node to output audio data packets 211, 212, . . . , 21 n,respectively, in predetermined order. These packets are called “bundles”and “one” bundle contains audio data of several channels, for example, amaximum of “8” channels. Each bundle is given a bundle number that doesnot overlap with other bundles. A node seeking to receive outputtedaudio data determines a target bundle from the bundle number andcaptures the bundle that contains audio data to be received, andretrieves audio data of a desired channel from the received bundle. Eachof the packets 211, 212, . . . , 21 n transmitted from each node mayoccasionally carry two or more bundles. Then, CobraNet provides a serialcommunication period in which a serial communication packet 220 can betransmitted, in an idle time interval within the transmission cycle 200,the idle time interval being provided after completion of output of allthe packets within one transmission cycle 200.

Thus, CobraNet enables serial communication using the idle time intervalprovided within the transmission cycle 200. However, since the band forserial communication is narrow by definition, the transmission ofcontrol data causes a problem of increasing delay time. In addition,since the delay time depends on the number of bundles of audio data, itis difficult to stably control many audio amplifiers and other audioequipment involved in the network, and to stably collect status data ofthe amplifiers and other audio equipment from the network.

For such reasons, the serial communication packet 220 defined in theCobraNet protocol is not so often used in practice. Instead, QSControl(trademark) and Audia (trademark) are known for example as technology oftransmitting control data to a system to which CobraNet is applied. Inthese technology, the control of each node, for example, the collectionand control of the states of the amplifiers, is performed through adedicated network for control data independent of the CobraNet network.

However, the use of the separate network independent of the CobraNetnetwork to control the amplifiers and the like requires physicalconnection for both CobraNet network and the separate network. Statedotherwise, an audio data network cable and a control data network cableare separately required to connect each node. This increases the numberof cables used and hence causes a problem of increasing the trouble inbuilding up the sound system.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoingcircumstances, and it is an object of the invention to provide a signaltransmission apparatus capable of stably monitoring and controllingaudio amplifiers and other audio equipment through a narrow-bandtransmission line of control data.

In solving the above-mentioned problems, the present invention comprisesthe following structures. Namely, in a first aspect of the invention, asignal transmission apparatus is connected to a network as one nodeamong a plurality of nodes involved in the network which is providedwith an audio signal transmission period for transmitting a plurality ofchannels of audio signals each transmission cycle and a control datatransmission period for transmitting control data of the plurality ofthe nodes each control cycle by using an idle time period other than theaudio signal transmission period. The signal transmission apparatuscomprises a storage section that stores configuration information ofsaid one node, the configuration information representing a settingstate of said one node, a transmitting section that transmits thecontrol data including an error checking code of the configurationinformation, the error checking code being a code data for checking anerror of the configuration information, and a control section thatdetermines whether the configuration information contains an informationblock to be transmitted, and operates in case that the configurationinformation is determined to contain the information block to betransmitted for controlling the transmitting section to transmit theinformation block together with the error checking code.

Preferably, the signal transmission apparatus further comprises areceiving section that receives an error checking code from another nodethrough the network, the error checking code being a code data forchecking an error of configuration information representing a settingstate of said another node, wherein the storage section further storesconfiguration information of all the nodes including said another nodetogether with error checking codes corresponding to the respectiveconfiguration information, and wherein the control section includes acomparison subsection that compares the received error checking code ofsaid another node with the stored error checking code corresponding tosaid another node so as to detect an inconsistency between the receivederror checking code and the stored error checking code, such that thecontrol section operates when the inconsistency is detected forcontrolling the transmitting section to transmit the control datacontaining request data to said another node, the request datarequesting said another node for transmission of an information block ofthe configuration information associated to the received error checkingcode.

Preferably, in the signal transmission apparatus, the receiving sectioncan receive request data from another node, the request data requestingsaid one node for transmission of an information block of theconfiguration information of said one node, such that the controlsection operates upon the receiving of the request data for controllingthe transmitting section to transmit the information block to saidanother node.

Preferably, in the signal transmission apparatus, the plurality of thenodes involved in the network sequentially transmit the control dataaccording to a predetermined transmission order within the control datatransmission period, such that the control section controls thetransmitting section to transmit the control data at a timing when saidone node comes in turn of the predetermined transmission order.

In a second aspect of the invention, a signal transmission apparatus isconnected to a network as one node among a plurality of nodes involvedin the network which is provided with an audio signal transmissionperiod for transmitting a plurality of channels of audio signals eachtransmission cycle and a control data transmission period fortransmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period. The signal transmission apparatus comprises atransmitting section that transmits the control data in the control datatransmission period, and a control section including a list creationsubsection that creates a transmission order list determining atransmission order of the plurality of the nodes within one controlcycle for sequentially transmitting the control data, the controlsection controlling the transmitting section to transmit the controldata including the created transmission order list for distributing thetransmission order list to all of the nodes involved in the network.

Preferably, the control section includes a monitoring subsection thatmonitors whether all the nodes sequentially transmit the control dataaccording to the determined transmission order, and an instructionsubsection that detects a failed node which does not transmit thecontrol data despite reaching a turn of the determined transmissionorder and instructs a node immediately subsequent to the failed node inthe determined transmission order to transmit the control data, and thelist creation subsection operates when the failed node is detected forcreating a new transmission order list from which the failed node iseliminated.

Preferably, the control section includes a new node detection subsectionthat detects whether a new node is added to the network, such that thelist creation subsection operates when the new node is detected forcreating a new transmission order list to which the new node is added.

Preferably, said one node is selected as a sole commander node among theplurality of the nodes connected to the network for commanding all thenodes.

Preferably, each of the nodes involved in the network sequentiallytransmits the control data at each timing when each node comes in turnof the transmission order determined by the distributed transmissionorder list.

In a third aspect of the invention, a signal transmission apparatus isconnected to a network as one node among a plurality of nodes involvedin the network which is provided with an audio signal transmissionperiod for transmitting a plurality of channels of audio signals eachtransmission cycle and a control data transmission period fortransmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period, said one node being connected to a control deviceseparately from the network. The signal transmission apparatus comprisesa storage section that stores configuration information of all the nodesinvolved in the network including said one node and other nodes, theconfiguration information representing a setting state of each node, aninput section that receives a change instruction from the control devicefor instructing a change of the stored configuration information, adetermination section that determines whether the change instruction isto instruct a change of the configuration information associated to saidone node, and a transmitting section operative in case that the changeinstruction is determined to instruct the change of the configurationinformation associated to other node than said one node, fortransmitting the control data containing instruction data to said othernode without changing the configuration information of said one node,the instruction data enabling said other node to execute the change ofthe configuration information associated to said other node according tothe change instruction.

Preferably, the signal transmission apparatus further comprises anupdate section operative in case that the change instruction isdetermined to instruct the change of the configuration informationassociated to said one node, for updating the configuration informationof said one node stored in the storage section, and wherein thetransmitting section transmits the control data containing change datarepresenting a content of the updated configuration information to othernodes. For example, said one node is connected to an audio processingdevice for processing the audio signals according to a part of thestored configuration information, and the update section operates incase that the change instruction instructs the change of the part of theconfiguration information associated to the audio processing device, forchanging the setting state of the audio processing device according tothe change instruction.

Preferably, the signal transmission apparatus further comprises areceiving section that receives from other node change data indicating acontent of the configuration information changed at said other node, andan update section that changes a content of the configurationinformation of said other node stored in the storage section accordingto the received change data.

Preferably, the plurality of the nodes involved in the networksequentially transmit control data according to a predeterminedtransmission order within the control data transmission period, suchthat the transmitting section transmits the control data at a timingwhen said one node comes in turn of the predetermined transmissionorder.

In a fourth aspect of the invention, a control apparatus is connected toone node among a plurality of nodes involved in a network which isprovided with an audio signal transmission period for transmitting aplurality of channels of audio signals each transmission cycle and acontrol data transmission period for transmitting control data of theplurality of the nodes each control cycle by using an idle time periodother than the audio signal transmission period. The control apparatuscomprises a storage section that stores configuration information of allthe nodes involved in the network, the configuration informationrepresenting a setting state of each node, a display section thatdisplays a content of the configuration information stored in thestorage section, a changing section operative when a change operation isperformed for rewriting a content of the stored configurationinformation as instructed by the change operation, an output sectionthat feeds a change instruction to said one node in response to thechange operation for effectuating a change of the configurationinformation in one or more node of the network, an input section thatreceives change data fed back from said one node, the change datarepresenting a changed result of the configuration informationeffectuated in one or more node of the network, and a determinationsection that determines whether the changed result represented by thereceived change data matches or mismatches the rewritten content of thestored configuration information, and that issues a warning in case thatthe changed result of the configuration information mismatches therewritten content of the stored configuration information.

Preferably, the display section updates the displaying of the storedconfiguration information based on the change operation such that therewritten content of the configuration information is displayed in avisually different mode than a visually normal mode by which othercontents than the rewritten content are displayed. Further, the displaysection returns the rewritten content of the configuration informationfrom the visually different mode to the visually normal mode when theinput section receives the change data fed back from said one node.Moreover, the changing section overwrites the rewritten content of thestored configuration information according to the change data fed backfrom said one node.

Preferably, the control apparatus further comprises a setting sectionthat sets an operation mode for determining whether to issue the warningor not, such that the warning is issued on the condition that theoperation mode is set to issue the warning and the mismatch isdetermined by the determination section.

In a fifth aspect of the invention, a signal transmission apparatus isconnected to a network as one node among a plurality of nodes involvedin the network which is provided with an audio signal transmissionperiod for transmitting a plurality of channels of audio signals eachtransmission cycle and a control data transmission period fortransmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period. The signal transmission apparatus comprises a firstdetermination section that determines whether a predetermined timeperiod has elapsed since the start of a current control cycle, a seconddetermination section that determines whether the transmission of thecontrol data from all the nodes is completed in the current controlcycle, and a cycle starting section that transmits a start signal to allof the nodes for starting a new control cycle when results ofdetermination by the first and second determination sections are bothaffirmative. Preferably, said one node is selected as a sole commandernode among the plurality of the nodes connected to the network forcommanding all the nodes. Preferably, the plurality of the nodesinvolved in the network sequentially transmit control data according toa predetermined transmission order within the control data transmissionperiod, such that said one node transmits the control data at a timingwhen said one node comes in turn of the predetermined transmissionorder.

Another signal transmission apparatus is connected to a network as onenode among a plurality of nodes which treat various physical quantitiesin processing of audio signals, the network being provided with an audiosignal transmission period for transmitting a plurality of channels ofaudio signals each transmission cycle and a control data transmissionperiod for transmitting control data of the plurality of the nodes eachcontrol cycle by using an idle time period other than the audio signaltransmission period. The signal transmission apparatus comprises acreating section that creates instruction data which instructs anothernode to transmit a particular one of the physical quantities treated bysaid another node, a transmitting section that transmits the controldata including the created instruction data to said another node throughthe network, and a receiving section that receives the control datacontaining a value of the particular physical quantity from said anothernode. Preferably, said one node is selected as a sole commander nodeamong the plurality of the nodes connected to the network for collectingthe values of the various physical quantities treated in the pluralityof the nodes.

A further signal transmission apparatus is connected to a network as onenode among a plurality of nodes which treat various physical quantitiesin processing of audio signals, the network being provided with an audiosignal transmission period for transmitting a plurality of channels ofaudio signals each transmission cycle and a control data transmissionperiod for transmitting control data of the plurality of the nodes eachcontrol cycle by using an idle time period other than the audio signaltransmission period. The signal transmission apparatus comprises areceiving section that receives the control data containing instructiondata form another node, the instruction data instructing said one nodeto transmit a first physical quantity and a second physical quantitytreated by said one node, and a transmitting section that transmits thecontrol data containing values of the first physical quantity and secondphysical quantity, such that the value of the first physical quantity istransmitted every control cycle, while the value of the second physicalquantity is transmitted at a control cycle immediately after a variationin the value of the second physical quantity is detected in said onenode. Preferably, the first physical quantity is variable at a highfrequency as compared to the second physical quantity, and the secondphysical quantity is variable at a low frequency as compared to thefirst physical quantity. Preferably, the plurality of the nodes involvedin the network sequentially transmit control data according to apredetermined transmission order within the control data transmissionperiod, such that said one node transmits the control data at a timingwhen said one node comes in turn of the predetermined transmissionorder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general block diagram of a signal transmission systemaccording to one preferred embodiment of the present invention.

FIGS. 2( a) and 2(b) are a block diagram of each node and a personalcomputer (PC), respectively, involved in FIG. 1.

FIGS. 3( a), 3(b) and 3(c) are a timing chart of the embodiment.

FIG. 4 is an illustration of data structure of the embodiment.

FIG. 5 is an illustration showing a display example on the PC.

FIG. 6 is a flow chart of a control data transmitting routine performedon each node.

FIG. 7 is a flow chart of a control data receiving routine performed oneach node.

FIGS. 8( a), 8(b) and 8(c) are a flow chart of processing programsrunning on each node and the PC.

FIG. 9 is a flow chart of a control data receiving routine performed onthe PC.

FIGS. 10( a), 10(b) and 10(c) are a flow chart of processing programsrunning on a conductor node.

DETAILED DESCRIPTION OF THE INVENTION 1. Structure of Embodiment 1.1.General Structure The general structure of a signal transmission systemaccording to one preferred embodiment of the present invention will nowbe described with reference to FIG. 1.

1000 designates an Ethernet network (where Ethernet is a registeredtrademark), which transmits packets among a plurality of nodes connectedto the network 1000. The nodes connected to the network 1000 are broadlydivided into two categories: “general-purpose I/O node” and “amplifierI/O node”. The former is a node type capable of outputting and inputtingaudio data through the network 1000, and the latter is a node type whichcan only receive audio data from the network 1000. On the network 1000,it is possible to connect up to “eight” general-purpose I/O nodes and“16” amplifier I/O nodes.

In the example shown, “two” general-purpose I/O nodes 1100 and 1200 and“two” amplifier I/O nodes 1500 and 1600 are connected to the network1000. Then, a microphone 1102 and a recorder 1104 are connected to thegeneral-purpose I/O node 1100, a mixer 1202 is connected to thegeneral-purpose I/O node 1200, and a microphone 1204 and a recorder 1206are connected to the mixer 1202.

On the other hand, two or more amplifiers 1502-150 n are connected tothe amplifier I/O node 1500 so that audio signals outputted from theseamplifiers will be sounded through loudspeakers 1512-151 n. Although thecable that connects the amplifier I/O node 1500 and each amplifier1502-150 n consists of a cable for transmitting analog audio signal fromthe node to each amplifier, and another cable for performingbidirectional transmission of control signals between the node and eachamplifier, it is respectively expressed by one line on the drawing forconvenience sake. Here, one amplifier I/O node can convert audio datafor a maximum of “16” channels into analog signals from among “four”bundles (“32” channels) of audio data, and output the analog signals,while it can carry out bidirectional transmission of control signals toand from a maximum of “32” amplifiers.

Similarly, the amplifier I/O node 1600 is connected to two or moreamplifiers 1602-160 n, and loudspeakers 1612-161 n are connected tothese amplifiers, respectively. In the embodiment, a personal computer(PC) for monitoring and control of the signal transmission system isalso connectable to one or more of the nodes. In the example shown, PCs1910 and 1920 are connected to the general-purpose I/O node 1100 and theamplifier I/O node 1600, respectively.

1.2. Structure of Each Node

Referring next to FIG. 2( a), the detailed structure of each node willbe described.

As shown in the figure, 102 designates a display that shows variouskinds of information to a user. 104 is an operator panel for settingvarious kinds of information. Since the display 102 and the operatorpanel 104 are of simple structure, detailed settings for each node ordisplay of the detailed settings are made through the PC 1910 or 1920.106 designates a unique I/O part that is constructed according to theapplication purpose of each node. For example, for each of thegeneral-purpose I/O nodes 1100 and 1200, an AD converter, a DAconverter, a digital I/O, etc. are provided in the unique I/O part 106so that a digital signal or analog signal can be inputted and outputtedto and from a mixer or the like. On the other hand, for each of theamplifier I/O nodes 1500 and 1600, a DA converter for supplying ananalog signal to each amplifier and a serial interface for exchanging acontrol signal with the amplifier are provided in the unique I/O part106.

110 designates a LAN I/O part that performs input and output of packetsof audio data and control data to and from the network 1000. 108 is aDSP that makes mutual conversions between an audio signal or controlsignal and an audio data packet or control data packet based on aprotocol to be described later. 116 is a PC I/O part, which performsdata communication with the PC when the above-mentioned PC 1910 or 1920is connected. 118 is a CPU that controls each part of the node through abus 112 based on a control program stored in a flash memory 120. 122 isa RAM that is used as a work memory of the CPU 118.

1.3. Structure of Each Personal Computer

Referring next to FIG. 2( b), the structure of each PC will bedescribed. As shown in the figure, 134 designates an input device thatis made up of a character-input keyboard with a mouse or the like. 136is a display unit that shows various kinds of information to the user.138 is a hard disk that stores programs, such as an operating system andan application program (to be described later in detail) for controllingthe signal transmission system. 140 is a CPU that controls the othercomponents through a bus 130 based on these programs. 142 is a ROM thatstores an initial program loader and the like. 144 is a RAM that is usedas a work memory of the CPU 140. 132 is a serial interface that isconnected to the PC I/O part 116 of either of the above-mentioned nodes.

2. Data Structure of Embodiment

Configuration information 400 shown in FIG. 4 is stored in the RAM 122of each node and the hard disk 138 or the RAM 144 of each PC asinformation for sharing the state of the signal transmission system.Then, the synchronous control of the configuration information 400stored at each node is carried out by performing processing to bedescribed later so that the identical contents will be shared among thenodes. The configuration information 400 is divided into “24” noderegions 400-1 to 400-24. As mentioned above, it is possible to connectup to “eight” general-purpose I/O nodes and “16” amplifier I/O nodes onthe network 1000. Therefore, “24” regions corresponding to the maximumnumber of nodes are pre-allocated, regardless of the actual number ofconnected nodes, in preparation for the case where the maximum number ofnodes are connected.

In the node region 400-1, 404 is an RO (Read Only) block for storingRead-only data that does not allow the PC to instruct any state change.406 to 410 are RW blocks for storing data that allow the PC to writedata for setting a state and read the data for checking the state.Further, 412 is a physical quantity block for storing various physicalquantities other than the temperature of a corresponding node, that is,input voltage to an amplifier, output voltage from the amplifier, outputpower of the amplifier, output impedance of the amplifier, etc. Thisphysical quantity block 412 is also the “Read Only” block that allowsonly the reading of data for checking the state. Further, 402 is a CRCblock for storing a CRC code (error-checking code) allotted to each ofthe above-mentioned blocks 404-410, and a MAC address of the nodeconcerned. In other words, CRC codes corresponding to respective blocks404 to 410, that is “four” kinds of CRC codes, are stored in the CRCblock 402.

Here, one of the node regions 400-1 to 400-24 of a certain noderepresents its own node information, and if it is 400-j, the node region400-j is called the “own node region.” Further, since the other noderegions 400-1 to 400-(j−1), and 400-(j+1) to 400-24 express the statesof the other nodes, they are called the “other node regions.”

Data stored in the above-mentioned blocks 404 to 410 vary according tothe kind of node. First suppose that the node region 400-1 is a regionassociated with a general-purpose I/O node. In this case, informationfor specifying the source of a word clock for the general-purpose I/Onode concerned is stored in the RO block 404. The bundle number of thebundle inputted and outputted from the node is stored in the RW block406. Correspondences between channels of analog or digital audio signalsinputted and outputted from the outside to the node concerned and netchannels (channels in the bundles inputted and outputted to and from thenetwork 1000) are stored in the RW block 408. The name (characterstring) of the general-purpose I/O node is stored in the RW block 410.

Suppose further that the node region 400-1 is a region associated withan amplifier I/O node. In this case, the temperature of each of theamplifiers connected to the node concerned, information as to whetherthe maximum “32” amplifiers controlled by the node are in an operablestate, and information as to whether a warning is outputted from any ofthese amplifiers are stored in the RO block 404. The bundle numbers ofup to “four” bundles (corresponding to 32 net channels) received by theamplifier I/O node concerned are stored in the RW block 406. Informationfor specifying the channel number of the DA converter corresponding toeach channel that is converted to an analog signal is stored in the RWblock 408. The name (character string) of the amplifier I/O node isstored in the RW block 410.

Then, among the physical quantities on each of the amplifiers connectedto the amplifier I/O node, infrequently-changing physical quantitiessuch as the temperature of each amplifier are stored in the RO block404, and frequently-changing physical quantities (voltage, impedance,etc.) are stored in the physical quantity block 412.

3. Data Transmission Protocol

As mentioned above in connection with FIG. 3( a), CobraNet allocates aserial communication period in each transmission cycle so that theserial communication packet 220 can be transmitted. Therefore, in theembodiment, a further upper layer (control layer) is formed from asequence of transmission cycles 200 to transmit various kinds of controlsignals through this control layer. A protocol for this control layerwill be described with reference to FIG. 3( b)

In the control layer, various kinds of control data are transmitted atintervals of 250 msec as “control cycle 240.” Then, one of the nodes isset as a special node (called the “conductor node”) for managing thecontrol cycle 240. The conductor node may be the above-mentioned“conductor” node or any other node. At the beginning of each controlcycle 240, the conductor node outputs a cycle start packet 250 to thenetwork 1000. Subsequently, control data packet bundles 251-254 areoutputted to the network 1000 one by one from the respective nodes.

The number of control data packet bundles is the same as the number ofnodes (“Four” in the example of FIG. 1) connected to the network 1000,and each node outputs a control data packet bundle once in each controlcycle 240. The first control data packet bundle 251 is a control datapacket bundle outputted from the conductor node. Therefore, the controldata packet bundle 251 is outputted immediately after the cycle startpacket 250 is outputted. On the other hand, the subsequent control datapacket bundles 252-254 are control data packet bundles outputted fromthe nodes other than the conductor node, and these packet bundles areoutputted at predetermined packet intervals in order to prevent acollision among packet bundles.

Each of the control data packet bundles consists of an event data packet260, a report packet 262, a physical quantity data packet 264, and aterminate packet 266. Among these, the report packet 262 and theterminate packet 266 are indispensable packets, and the other packetsare added as needed.

Since the control cycle 240 is set “250 msec” at the shortest interval,if the number of connected nodes increases as shown in FIG. 3( c), itwill become longer than “250 msec.” However, the period of the controlcycle 240 is never shorter than “250 msec.” This is because at least“250 msec” is pre-allocated as a time period for which each nodecollects its own node state every control cycle 240 to report it to theother nodes.

3.1. Cycle Start Packet 250

The details of each packet mentioned above will be described below. Thecycle start packet 250 consists of the following data:

(1) Output Sequence of Packet Bundles from Respective Nodes

As mentioned above, the control data packet bundles 251-254 areoutputted one by one from each node in the control cycle 240, and theoutput sequence of each node is specified in the cycle start packet 250.

(2) Listing of Physical Quantities to be Outputted from Each Node

As will be described later in detail, each node can transmit each of thecontrol data packet bundles 251-254 including physical quantities suchas the temperature, voltage, impedance, etc. of each of the amplifiersconnected to its own machine. Among the physical quantities to beoutputted, frequently-changing physical quantities are specified in theeven data packet 260 outputted primarily from a PC-connect node to whicha PC is connected. However, if each of the other nodes recognizes thephysical quantities to be outputted based on the event data packet 260from the PC-connect node, packet capturing loss may occur due to acommunication error etc. Therefore, in the embodiment, a “currentlydisplayed list” that is a list of physical quantities to be outputted isincluded in the cycle start packet 250 so that the conductor node willcollectively manage the specifications of physical quantities to beoutputted from each node.

3.2. Event Data Packet 260

The event data packet 260 consists of the following data:

(1) Instruction Data

As will be described later in detail, if a node transmitting a controldata packet bundle (hereinafter called a “transmit node”) is connectedto a PC, the user can instruct not only the transmit node but also allthe nodes through the PC to change all state settings (data stored inthe node regions RW blocks 406 to 410 of each node). In this case, statechanges are instructed from the transmit node to the other nodes inwhich the states should be changed. The data for giving the instructionsis called “instruction data.” When the state of a node to which the PCis connected (hereinafter called the PC-connect node) is changed by thePC, the instruction data is not outputted from the node concerned.Further, when a monitoring point of a physical quantity (a desiredphysical quantity at a desired node) is specified by the PC, themonitoring point is notified to the conductor node, and as mentionedabove, it is then notified to each of the other nodes through the cyclestart packet 250. Since any nodes other than the conductor node may bepromoted to the conductor node, it is advisable to store at each nodethe monitoring point notified from the PC or through the cycle startpacket 250.

(2) Change Data

When a node receives the instruction data and changes its node settings,the changed node settings are notified to all the nodes. When the nodeto which the PC is connected is instructed by the PC to change its ownnode settings, the changed node settings are also notified to the othernodes. Further, when a node detecting an infrequently-changing physicalquantity such as the “temperature” of an output-stage amplifier finds achange in the detected physical quantity, the changed physical quantityis notified to the other nodes. Data for making these notifications arecalled “change data.” In other words, when any data stored in the blocks404-410 of the own node region 400-j is changed, each node must notifyits state change to the other nodes by sending the change data. Thismust be performed so that the contents of the node region blocks 404-410of each node will be synchronized with those stored in the PC.

(3) Request Data

Suppose that the own node region of a first node is 400-j. In this case,if a contradiction arises between the contents of the CRC block 402 inany of the other node regions, 400-k (where k takes on values from 1 to(j−1) and (j+1) to 24) and the CRC calculation results of other blocks404 to 410 of node region 400-k, it means that an error has occurred inthe contents of blocks 404-410 of the other node region 400-k. In such acase, when the first node turns into the transmit node, it sends, to asecond node corresponding to the other node region 400-k in which theerror has occurred, a request to transfer a block(s) involved with theerror. Data for making such a request is called “request data.”

3.3. Report Packet 262

The report packet 262 consists of the following data:

(1) Contents of CRC Block 402 Related to Transmit Node

The CRC block 402 in the own node region 400-j of the transmit node isalways included in the report packet 262 and transmitted every controlcycle 240. Thus the report packet 262 is an indispensable packet and hasto be generated every control cycle 240. When receiving the CRC code,the other nodes can check whether the correct data related to thetransmit node is stored in the configuration information 400 on each ofthe other nodes.

(2) Contents of Other Blocks 404-410 Related to Transmit Node

As mentioned above, when data stored at a first node indicates that anerror has occurred in any of the blocks in the node region related to asecond node, request data is sent from the first node to the secondnode. After receiving the request data, once the second node has turnedinto the transmit node, the contents of the requested block are added tothe report packet 262.

3.4. Physical Quantity Data Packet 264

When a physical quantity to be outputted is specified by the cycle startpacket 250, the value of the physical quantity specified from among thefrequently-changing physical quantities, such as input voltage to anamplifier, output voltage of the amplifier, and the output impedance ofthe amplifier, is included in the physical quantity data packet 264, andoutputted every control cycle 240. As mentioned above, a change in“temperature” is transmitted as change data only when the change occurs.Since the “temperature” change does not often occur, an enormous amountof data will go to waste if the value of “temperature” is transmittedthrough the physical quantity data packet 264 every control cycle 240.Thus, from the point of view of reducing the total amount of transmitteddata, the value of “temperature” is transmitted only when it changes.

3.5. Terminate Packet 266

The terminate packet 266 is outputted in order to notify the other nodesof the completion of packet transmission by the current transmit node.

4. Operation of Embodiment 4.1. Control Data Transmission At Node (FIG.6)

The operation of the embodiment will next be described. First of all,when each node goes into a state in which each of the control datapacket bundles 251-254 is to be transmitted to the other nodes throughthe network 1000, a control data transmitting routine shown in FIG. 6 isstarted. The following three states (1), (2) and (3) can be specificallyconsidered to be “the transmission state” in which each of the packetbundles “is to be transmitted.”

(1) Immediately After Output of Cycle Start Packet 250:

The conductor node outputs the cycle start packet 250 every controlcycle 240 based on its own node clock. Such a conductor node outputs thecontrol data packet bundle 251 immediately after outputting the cyclestart packet 250.

(2) After Detection of Terminate Packet 266:

As mentioned above, the sequence or order by which each node outputs thecontrol data packet bundle is indicated in the cycle start packet 250.Therefore, the nodes other than the conductor node output their controldata packet bundles when a predetermined packet interval has elapsedafter the immediately preceding node outputted the terminate packet 266.

(3) When Receiving Instructions from Conductor Node:

The conductor node keeps track of whether each node is outputting thecontrol data packet bundle in the correct order. If a packet bundle tobe outputted from a correct node cannot be detected, the next nodedetermined in the output order will be instructed to output the packetbundle. In such a case, the node instructed outputs the control datapacket bundle immediately.

Then, when the processing proceeds to step SP6 in FIG. 6, it isdetermined whether there is any event data to be transmitted. In otherwords, when any state change (including a “temperature change” themeasurement of which has been instructed) has occurred at the transmitnode, the change data needs outputting. When any other node is requiredto change its state in accordance with instructions from the PC, theinstruction information needs outputting. Further, when a contradictionarises between the CRC codes, the request data needs outputting. If thecase falls into any of these categories, the answer to this step SP6 isdetermined as “YES” and the processing proceeds to step SP8. In stepSP8, the event data packet 260 is created based on corresponding eventdata and transmitted to the network 1000.

Then, when the processing proceeds to step SP10, it is determinedwhether any of the blocks 404-410 in the own node region 400-j is to betransmitted, that is, whether the “request data” is received from any ofthe other nodes. When the answer is “YES” here, the processing proceedsto step SP12, and one or more blocks for which the request data has beensent are listed as blocks to be included in the report packet 262.

Next, when the processing proceeds to step SP14, the CRC block 402 inthe own node region 400-j is added to the list of blocks to be includedin the report packet 262. Therefore, when the answer to step SP10 is“NO,” only the CRC block 402 is listed. Next, based on all listedblocks, the report packet 262 is created to include those contents.Next, the processing proceeds to step SP16 in which the created reportpacket 262 is outputted through the network 1000.

Next, when the processing proceeds to step SP18, the contents of the“currently displayed list” received from the conductor node are checked.In other words, since all the physical quantities to be outputted fromeach node are included in the “currently displayed list,” all “physicalquantities but temperature to be outputted from its own node” aresearched out. Next, the processing proceeds to step SP20, and it isdetermined based on the check results in step SP18 whether there is anyphysical quantity to be transmitted. If the answer is “YES” here, theprocessing proceeds to step SP22, in which the physical quantity datapacket 264 is created based on the physical quantity to be transmittedand outputted to the network 1000. Next, the processing proceeds to stepSP24 in which the terminate packet 266 is outputted to the network 1000.The routine is ended after the above processing step.

4.2. Control Data Reception at Node (FIG. 7)

Next, when any control data packet bundle is received at any of thenodes other than the transmit node through the network 1000, a controldata receiving routine shown in FIG. 7 is started at each node (receivenode) that has received the packet bundle. As shown, when the processingproceeds to step SP32, it is determined whether the PC is connected tothe own node PC I/O part 116. When the answer is “YES” here, theprocessing proceeds to step SP34 in which various kinds of control dataare transferred to the PC. The control data transmitted to the PC areclassified into “data to be transmitted immediately,” and “data to betransmitted after a predetermined waiting period has elapsed,” andtransmitted at proper timings according to this classification. Theclassification method for the control data and the criteria forclassifying will be described later.

Next, the processing proceeds to step SP36, and it is determined whetherthe “request data” to the own node is included in the packet bundlereceived. If the answer is “YES” here, the processing proceeds to stepSP38, in which the transmission of a block requested from among theblocks 404-410 in the own node region 400-j is prepared. In other words,if the own node turns into the transmit node in the next cycle, theblock requested at this time will be added to one or more blocks to beincluded in the report packet 262 at the above-mentioned processing stepSP12.

Next, the processing proceeds to step SP40, and it is determined whetherthe “instruction data” to the own node is included in the packet bundlereceived. If the answer is “YES” here, the processing proceeds to stepSP42, in which the contents of the own node region 400-j are alteredbased on the “instruction data.” For example, if the instruction data isto change the state of any of the amplifiers connected to the own node,a control signal is outputted to the amplifier and the like to realizesuch a state change. Next, the processing proceeds to step SP44, inwhich the transmission of the altered contents of the own node region400-j is prepared. In other words, if the own node turns into thetransmit node in the next cycle, the currently altered contents of theown node region 400-j will be added to the change data to be included inthe event data packet 260 at the above-mentioned processing step SP8.

Next, the processing proceeds to step SP46, and it is determined whetherthe “change data” from the transmit node is included in the packetbundle received. If the answer is “YES” here, the processing proceeds tostep SP47, in which the contents of a node region 400-k (where k takeson values from 1 to 24) related to the transmit node are altered basedon the change data.

Next, the processing proceeds to step SP48, and it is determined whetherany of the blocks 404-410 is included in the report packet 262 received.If it is included, the contents of the received block is written overthe corresponding contents in the node region 400-k related to thetransmit node. Then, a CRC code corresponding to the altered contents ofthe changed block 404-410 (that is, the block changed at step SP47 orthe block overwritten at step SP48) is calculated, and the calculatedCRC code is written over a corresponding portion of the CRC block 402. Acommon operational formula is used for all the nodes and the PC at thecalculation of CRC code, so that any CRC code in the CRC block 402 isuniquely determined once the contents of the blocks 404-410 aredetermined.

Next, the processing proceeds to step SP50, and it is determined whetherthe physical quantity data packet 264 is included in the packet bundlereceived. If it is included, the contents of the packet is written overthe physical quantity block 412 in the node region 400-k of the transmitnode. Next, the processing proceeds to step SP54, in which CRC codesstored in the CRC block 402 of the node region 400-k related to thetransmit node are compared with corresponding CRC codes supplied fromthe transmit node (included in the report packet 262), respectively.

Next, the processing proceeds to step SP56, and it is determined whethera mismatch is found between the stored CRC codes and the suppliedcorresponding CRC codes. If a mismatch is found therebetween, it meansthat incorrect information is stored in the block related to themismatched CRC code. If the answer is “YES” here, the processingproceeds to step SP58, in which request data for requesting the transmitnode to retransmit the block concerned is created and a messageindicating the occurrence of a communication error is displayed on thedisplay 102. This request data is outputted at the above-mentioned stepSP8 when the own node turns into the transmit node in the next cycle.

If the mismatch between the CRC codes occurs in the RO block 404, themessage indicating the communication error may not be displayed on thedisplay 102. On the other hand, no CRC codes are created for thephysical quantity block 412. Therefore, even if wrong contents arestored in the physical quantity block 412 due to a communication erroror the like, the erroneous state will continue until the block isupdated in the next or later cycle. Thus the frequency of outputtingrequest data can be reduced to minimize the total amount of control dataon the network 1000.

A new node is hot-pluggable to the network 1000. In this case, allregions but the own node region 400-j in the configuration information400 of the new node are filled with blanks, and a CRC code indicatingthat each block is empty is recorded in the CRC blocks 402 of theregions other than the own node region. Therefore, since the CRC coderecorded on the new node never matches with any other CRC codes receivedfrom the other nodes on the network 1000, the retransmission of theconfiguration information (blocks 404-410) representing the all statesettings related to the transmit node is requested each time the newnode receives a CRC code from any of the other nodes. Such a requestallows the new node to receive the configuration information on all thenodes sequentially from the other nodes. Then, since the receivedinformation is recorded on the new node as the configuration information400, the new node can automatically hold the configuration informationof all the nodes on the network 1000.

4.3. Connection of PC

When the PC 1910 or 1920 is connected to any node and a predeterminedapplication program is started on the PC, a “transfer command” is firstexecuted. Then, when the command is executed, the configurationinformation 400 stored at the PC-connect node is transferred to the PC.This allows the PC to show various screens so that the user can refer tothe configuration information 400. Thus the user can grasp the state ofthe signal transmission system and instruct a state change(s) throughthese screens.

4.4. Screen Select Event (FIG. 8(a) and FIG. 5)

The above-mentioned application program allows the user to select anddisplay any of the various screens (windows) using the input device 134so as to look into the configuration information 400 stored in the PC.The occurrence of this screen select event invokes a screen select eventgenerating routine. As shown in FIG. 8( a), when the processing proceedsto step SP70, it is determined whether the selected screen is a screenfor displaying physical quantities (temperature, voltage, impedance,etc.).

When the answer is “YES” here, the processing proceeds to step SP72 inwhich the selected screen is displayed on the display unit 136. Next,the processing proceeds to step SP74 in which a specification event forspecifying physical quantities to be displayed on the screen istransmitted. If the answer to step SP70 is “NO,” the processing proceedsto step SP76 in which the selected screen is displayed on the displayunit 136. Next, the processing proceeds to step SP78 in which variousother kinds of processing are executed and the routine is ended.

Here, a screen for displaying the “physical quantities” will bedescribed by taking as an example a group display screen (see FIG. 5) onwhich two or more channels of amplifiers connected to amplifier I/O nodeare grouped and the operating state of the two or more channels aredisplayed on a group basis. First, in the embodiment, the monitoringpoints of physical quantities are classified into two or more “groups.”In the figure, 350 to 354 designate tags and the user can click on anytag to select a corresponding group. 300 designates a display window forshowing the physical quantities belonging in the selected group. 300-1,300-2, . . . designate monitoring point frames, and each monitoringpoint frame indicates two or more physical quantities each correspondingto a monitoring point.

In the monitoring point frame 300-1, 302 is a channel indication partthat indicates a character string specifying to which channel theindications in the monitoring point frame 300-1 are made, for whichamplifier the channel is, and to which amplifier I/O node the amplifieris connected. In the character string “AN1-3-2,” the first twoalphabetical letters “AN” denotes an “amplifier I/O node,” and the firstnumber immediately after “AN” denotes the serial number of the“amplifier I/O node.” The second number “3” denotes the serial number ofan amplifier connected to the amplifier I/O node, and the last numberdenotes the channel number of the amplifier.

304 designates a name indication part that indicates a character stringrepresenting the name of the amplifier assigned by the amplifiermanufacturer. 306 is a power button for switching the power of theamplifier between the “ON” state and the “STAND-BY” state, indicating acharacter string representing the state. 308 is a channel nameindication part that indicates any channel name (character string)designated by the user. 310 is a protection indication part. Nothing isindicated in this part in a normal operation, but the character string“PROTECT” is indicated when an amplifier protection system is activated.

312 is an output clip indication part that lights up when an outputsignal for the channel concerned is clipped. 314 is a power output meterthat indicates the output level (“power” or “voltage”) of the outputsignal. 316 is an impedance indicator that indicates the numerical valueof load impedance of the channel concerned. 318 is a temperature meterthat indicates the temperature of an output-stage amplifier for thechannel concerned. 320 is an input meter that indicates the input levelto the channel concerned in decibels. 322 is an ATT fader indicates thesetting state of the attenuation factor of the input signal to thechannel. The ATT fader can also be used to change setting state of theattenuation factor by dragging it with the mouse.

324 is a phase button that switches the output phase of the channelbetween “NORMAL” and “REVERSE” with the click of the mouse. 326 is amute button that toggles the mute (attenuation of output level) on andoff for the channel with the click of the mouse. Among theabove-mentioned indication contents, those of the power output meter314, the impedance indicator 316, and the input meter 320 are based onthe contents stored in the physical quantity block 412 in the own noderegion 400-j of the amplifier I/O node, while the indication of thetemperature meter 318 is based on the RO block 404. The other indicationcontents are based on any of the RW blocks 406-410. In other words, theamplifier I/O node collects various setting states and physicalquantities from the amplifiers connected, and stores the contents in theown node region 400-j of the amplifier I/O node concerned. Then, whenthe contents of the region are reflected in the configurationinformation 400 on the PC through the PC-connect node, the contents ofthe display window 300 on the PC are updated.

The monitoring point frame 300-2 and the like have the same indicatorstructure as the monitoring point frame 300-1. The user has the optionof selecting an amplifier channel belonging to each group. In addition,different nodes and different amplifier channels can be shown in thesame display window 300.

4.5. Setting Change Event (FIG. 8(b))

As mentioned above, the user can operate the PC to control the settingstate of each part. In the example of FIG. 5, the setting statecorresponding to the ATT fader 322, for example, for a certain channelof an amplifier I/O can be changed by dragging the ATT fader 322 withthe mouse. Thus, when an event for changing the state of any node (or anamplifier(s) connected to the node) occurs, a setting change eventgenerating routine shown in FIG. 8( b) is started on the PC.

As shown, when the processing proceeds to step SP80, the configurationinformation 400 in the PC concerned is changed as instructed. Forexample, suppose that the attenuation factor is set to “10 dB” with theoperation of the ATT fader 322. In this case, data indicating “10 dB” isimmediately written in a portion corresponding to the amplifier channelconcerned in any of the RW blocks 406-410 in the node region related tothe amplifier I/O node concerned. Then, a CRC code corresponding to theupdated block is recalculated, and the calculation results are writtenin a corresponding portion of the CRC block 402. Next, the processingproceeds to step SP82 in which the indication contents are updated onthe PC based on the updated configuration information 400. In otherwords, in the above-mentioned example, the “knob” or control of the ATTfader 322 is moved to a position corresponding to “10 dB.”

At this time, however, since it is not checked that the amount ofattenuation of the channel corresponding to an actual amplifier has beenset to “10 dB,” the indication is made in the indication part (ATT fader322 in this case) in a different manner from its normal state (forexample, the ATT fader 322 is grayed out or flashes) to indicate thatthe change is unconfirmed. Next, the processing proceeds to step SP84 inwhich change instructions indicating the changed contents (target nodeand amplifier, kind of parameter, amount of change, etc.) aretransmitted from the PC to the PC-connect node.

4.6. Setting Change Event (FIG. 8(c))

When receiving the change instructions, the PC-connect node runs achange instruction receiving routine shown in FIG. 8( c). As shown, whenthe processing proceeds to step SP90, it is determined whether thechange instructions received are directed to its own node (or anamplifier or the like connected to its own node). If the answer is “YES”here, the processing proceeds to step SP96 in which a correspondingportion of the own node region 400-j of the PC-connect node concerned ischanged.

If the changed portion is in any of the blocks 404-410, a CRC coderelated to the block concerned is recalculated, and written over acorresponding portion of the CRC block 402. On the other hand, if thechange instructions received are directed to an amplifier or the likeconnected to its own node, the setting state of the amplifier or thelike is also changed. Then, change data representing the contents ofchange concerned is created, and transmitted to the PC which isconnected to the PC-connect node. Further, when the PC-connect nodeturns into the transmit node, the change data is included in the eventdata packet 260 and transmitted to the other nodes (step SP8 in FIG. 6).

On the other hand, when the answer to step SP90 is “NO,” the processingproceeds to step SP92. Here, instruction data for instructing the othernode to change the state is created. In this case, the contents of theconfiguration information 400 are not changed. In other words, when thePC-connect node turns into the transmit node, the instruction data istransmitted to the other nodes to change the state (step SP8 in FIG. 6)so that the configuration information 400 will be changed at the othernodes (steps SP 42 and SP44 in FIG. 7). Then, when any of the othernodes turns into the transmit node, change data corresponding to thechanged state is transmitted from the node concerned to the PC-connectnode and the other nodes (step SP8 in FIG. 6). Thus, when receiving thechange data (change data related to the changed portion instructed bythe instruction data in step SP92), the PC-connect node concernedchanges a corresponding portion of the stored configuration information400 (step SP47 in FIG. 7).

Next, the processing proceeds to step SP94 to start measuring apredetermined period of time. Here, the “predetermined period of time”corresponds, for example, to “four cycles” when the mean value of pastcontrol cycles 240 is set as “one cycle.” As mentioned above, when aPC-connect node transfers control data received from the network 1000 tothe PC, the control data are classified into “data to be transferredimmediately” and “data to be transferred after a predetermined waitingperiod has elapsed.” Here, the “data to be transmitted after apredetermined waiting period has elapsed” denotes the “change datarelated to the changed portion instructed by the instruction data instep SP92,” and the “predetermined period of time” is the “predeterminedperiod of time (for example, four cycles) for which time measurement isdone at step SP94.”

A reason for putting pause to the transfer of data in this way will bedescribed below. First, possible problems that may arise if the transferis performed without standby time will be described. In the example ofFIG. 1, the PC 1910 is connected to the general-purpose I/O node 1100,and the PC 1920 is connected to the amplifier I/O node 1600. Supposehere that the display window 300 shown in FIG. 5 is displayed on both ofthe PCs 1910 and 1920. Suppose further that the monitoring point frame300-1 in the window is related to the second channel of the amplifier1502 connected to the amplifier I/O node 1500. Here, for example, if theATT fader 322 is set to “10 dB” on the PC 1910, and after a time lag(some 100 msec), the ATT fader 322 is set to “20 dB” on the PC 1920, thefollowing behavior is expected:

(1) First, when an operation event for setting the ATT fader 322 to “10dB” is detected on the PC 1910, change instructions are transmitted tothe general-purpose I/O node 1100.

(2) In response to the change instructions, when the own node for thegeneral-purpose I/O node 1100 turns into the transmit node, instructiondata for instructing the amplifier I/O node 1500 to “set 10 dB for theattenuation factor of the second channel of the amplifier 1502” istransmitted to the amplifier I/O node 1500.

(3) Here, when an operation event for setting the ATT fader 322 to “20dB” is detected on the PC 1920, change instructions are transmitted tothe amplifier I/O node 1600.

(4) The amplifier I/O node 1500 controls the amplifier 1502 based on theinstruction data from the general-purpose I/O node 1100, and updates theconfiguration information 400. As a result, change data indicating that“the attenuation factor of the second channel of the amplifier 1502 hasbeen set to 10 dB” is outputted to each of the other nodes.

(5) When receiving the change data, the amplifier I/O node 1600transfers to the PC 1920 the change data indicating that “theattenuation factor of the second channel of the amplifier 1502 has beenset to 10 dB.”

(6) Next, when the amplifier I/O node 1600 turns into the transmit node,instruction data for instructing the amplifier I/O node 1500 to “set 20dB for the attenuation factor of the second channel of the amplifier1502” is transmitted to the amplifier I/O node 1500.

(7) The amplifier I/O node 1500 controls the amplifier 1502 based on theinstruction data from the amplifier I/O node 1600, and updates theconfiguration information 400. As a result, change data indicating that“the attenuation factor of the second channel of the amplifier 1502 hasbeen set to 20 dB” is outputted to each of the other nodes.

(8) When receiving the change data, the amplifier I/O node 1600transfers to the PC 1920 the change data indicating that “theattenuation factor of the second channel of the amplifier 1502 has beenset to 20 dB.”

From the point of view of the PC 1920 on the above-mentioned sequence ofoperations, it receives the change data indicating that “the attenuationfactor has been set to 10 dB” and then the change data indicating that“the attenuation factor has been set to 20 dB” despite the fact that thesetting of the attenuation factor to 20 dB was instructed on the PC1920. As will be described later in detail, after change instructions tochange any portion of the configuration information 400 are transmittedto the PC-connect node, each PC keeps track of whether the state of thecorresponding portion is changed based on the change data in accordancewith the change instructions. Therefore, when being supplied with thechange data on “10 dB” with respect to the change instructions on “20dB,” the PC 1920 considers that a communication error has occurred, anda warning about the communication error is given on the PC 1920.

Thus, if no standby time is provided for the transfer of change datacorresponding to change instructions, a warning about “occurrence of anerror” is frequently given during configuration of the signaltransmission system despite the fact that no actual transmission errorhas occurred. Therefore, in the embodiment, change data corresponding tochange instructions is transferred after a predetermined waiting periodhas elapsed. The “predetermined period of time (e.g., four cycles)” isequivalent to an “estimated value of a time interval after output ofchange instructions to the nodes other than the PC-connect node from thePC to the PC-connect node until change data corresponding to the changeinstructions is received.”

Further, the meaning of “waiting or putting pause to” is different fromthe meaning of simply delaying.” It means that “when two or more kindsof change data on a corresponding portion are received during standbytime, the change data received at the end of the standby time istransferred.” In the above-mentioned example, although the PC 1920sequentially receives change data on “10 dB” and “20 dB,” if thesechange data are received during standby, only the last change data on“20 dB” is transmitted to the PC 1920. Thus, since the PC 1920 receivesthe change data on “20 dB” with respect to the change instructions on“20 dB,” no contradiction arises between the change instructions and thechange data.

On the other hand, the PC 1910 also receives change data on “10 dB” and“20 dB” in this order. If the standby time expires after receiving thechange data on “10 dB,” since the PC 1910 receives the change data on“10 dB” with respect to the change instructions on “10 dB,” nocontradiction will also arise between the change instructions and thechange data. After that, although the PC 1910 receives the change dataon “20 dB,” this is received as change data that does not correspond tothe previously-received change instructions. Thus, in the embodiment,since a predetermined waiting period is provided for the transfer toeach PC of the change data on a portion related to the changeinstructions, when instruction data is transmitted from both themultiple PCs as mentioned above, or when any of the other nodestransmits “request data for requesting a block including data to changethe instruction data” immediately after transmission of the instructiondata from the PCs, no error is detected, reducing the frequency ofoccurrence of errors.

4.7. PC Processing Upon Receiving Control Data (FIG. 9)

When the control data is supplied from the PC-connect node to the PC inthe above-mentioned processing step SP34 (FIG. 7), a control datareceiving routine shown in FIG. 9 is started on the PC. As shown, theprocessing proceeds to step SP100, and it is determined whether changedata is included in the control data. If the answer is “YES” here, theprocessing proceeds to step SP101. In step SP101, it is determinedwhether change instructions previously outputted to the PC-connect node(step SP84 in FIG. 8( b)) include change instructions, the results ofwhich are unconfirmed. When the answer is “YES” here, the processingproceeds to step SP102, and “change data corresponding to the previouslyoutputted change instructions” that is, “change data receivedimmediately after the change instructions and related to a portioninstructed by the change instructions” is searched for from among allthe change data received. Next, the processing proceeds to step SP103,and it is determined whether there is “change data corresponding to thechange instructions.

When the answer to step SP103 is “YES,” the processing proceeds to stepSP104. In step SP104, it is determined whether the contents of thechange data match the contents of the previously-outputted changeinstructions. Here, the determination that they “match” with each otherindicates that the parameters are changed in accordance with the changeinstructions, while the determination that they “do not match” with eachother indicates that the parameters are not changed in accordance withthe change instructions. If the answer is “NO (mismatch)” here, theprocessing proceeds to step SP106. In step SP106, a warning that “thechange data is different in content from the change instructions” isgiven (for example, a pop-up window is displayed). In other words, anoperation mode for determining whether such a warning display is madecan be preset on the PC. Thus, the warning display is made only when theoperation mode for making such a display is preset.

As described in step SP80 (FIG. 8( b)), the configuration information400 on the PC has already been updated to indicate the contents in whichthe change instructions is reflected. Therefore, a matchingdetermination in step SP104 may be made by comparing data (the contentsof the blocks 404-410 and the change data), or by comparing CRC codes(the CRC code in the CRC block 402 and a CRC code newly determined basedon the change data).

When the answer to step SP101 or SP103 is “NO,” or when the answer tostep SP104 is “YES,” or after completion of the warning processing atstep SP106, the processing proceeds to step SP108 in which the contentsof the configuration information 400 in the PC are changed based on thechange data received. In other words, not only the contents of theblocks 404-410 in the node region 400-k of the transmit node, but alsothe corresponding CRC code in the CRC block 402 are updated. Since theprocessing step SP108 is executed regardless of the determinationresults in step SP104, even if a contradiction arises between the changeinstructions and the change data, the change data will always beconsidered correct. The display state on display unit 136 is alsoupdated based on the change data.

As previously described in step SP82 (FIG. 8( b)), the indication thatindicates settings corresponding to unconfirmed change instructions wasmade in a different manner from the normal state. Therefore, if datacorresponding to the unconfirmed change instructions is included in thechange data received in the current cycle, the unconfirmed indicationstate is returned to the normal indication state.

Next, the processing proceeds to step SP109, and it is determinedwhether any of the blocks 404-410 is included as the report packet 262in the previously-received control data. If included, the contents ofthe block received is written over a corresponding portion in the noderegion 400-k related to the transmit node. Then, a CRC code iscalculated for the block changed from among the blocks 404-410 (that is,the block changed in step SP108 or the block overwritten in step SP109),and the calculated CRC code is written over a corresponding portion inthe CRC block 402.

Next, the processing proceeds to step SP110, and it is determinedwhether the data on the display unit 136 is updated by data updating inthe immediately preceding step SP109 (that is, data updating based onthe report packet 262). If the answer is “YES” here, the processingproceeds to step SP112, and the displayed contents of the data isupdated based on the control data received in this cycle. Next, theprocessing proceeds to step SP116 in which the two or more CRC codesstored in the CRC block 402 are compared with corresponding two or moreCRC codes (included in the report packet 262) supplied from the transmitnode, respectively. Next, the processing proceeds to step SP118, and itis determined whether there is a mismatch between CRC codes. If theanswer is “YES” here, the processing proceeds to step SP124, and theoccurrence of a mismatch between CRC codes is indicated on the displayunit 136. The indication may be made to determine a block in which amismatch has occurred.

Next, the processing proceeds to step SP126. In step SP126, a requestfor retransmission of data on a portion in which a mismatch between CRCcodes has occurred is outputted to the PC PC-connect node.

Next, the processing proceeds to step SP119, and it is determinedwhether the physical quantity data packet 264 is included in the controldata received. If included, the contents of the packet are written overthe physical quantity block 412 in the node region 400-k of the transmitnode. Next, the processing proceeds to step SP120, and it is determinedwhether any of frequently-changing physical quantities is currentlydisplayed on the display unit 136. If the answer is “YES” here, theprocessing proceeds to step SP122 in which the displayed contents areupdated based on the physical quantities stored in the configurationinformation 400. Here, from among the physical quantities currentlydisplayed, frequently-changing physical quantities are specified in thecurrently-displayed list in the cycle start packet 250. In other words,the physical quantities to be updated on the display screen are thephysical quantities transferred as the physical quantity data packetfrom the corresponding transmit node according to the currentlydisplayed list. In addition, since infrequently-changing physicalquantities are stored in the RO block 404 in each node region, theirdisplayed contents are updated in step SP108 or SP112.

4.8. Processing at Conductor Node 4.8.1. Failure Detection of ExistingNode

The conductor node keeps track of whether each of the other nodes istransmitting each control data packet bundle in the correct transmissionsequence as instructed in the cycle start packet 250. After output ofthe terminate packet 266 from a first node, if no control data packetbundle is not outputted from a second node within a predetermined periodof time, it can be considered that any failure has occurred to thesecond node (such as disconnection from the network 100). This secondnode is called the “failed node.”

In such a case, the conductor node invokes a failed node detectingroutine shown in FIG. 10( a). As shown, the processing proceeds to stepSP130, and it is determined whether the failed node is the last node inthe transmission sequence. When the answer is “NO” here, the processingproceeds to step SP132 in which a node immediately subsequent to thefailed node is instructed to transmit a control data packet bundle.Next, the processing proceeds to step SP134 in which the transmissionsequence is updated to eliminate the failed node. In other words, atransmission sequence list corresponding to a new transmission sequenceis created to eliminate the failed node from the original transmissionsequence. Therefore, each node outputs each control data packet bundleaccording to the new transmission sequence in the next control cycle240.

4.8.2. Additional Detection of New Node

As mentioned above, any new node is hot-pluggable to the network 1000.Since a short idle time is provided at the end of each control cycle240, the new node can inform the conductor node within the idle timethat “its own node has been connected.” Upon receipt of thisinformation, the conductor node invokes a node connection detectingroutine shown in FIG. 10( b). As shown, when the processing proceeds tostep SP140, the transmission sequence is changed to add the new node. Inother words, a transmission sequence list corresponding to a newtransmission sequence is created to add the new node to the originaltransmission sequence. Therefore, each node outputs each control datapacket bundle according to the new transmission sequence in the nextcontrol cycle 240. In addition to the node newly connected to thenetwork, any other nodes that are not included in the transmissionsequence indicated in the cycle start packet 250 may also be processedas new nodes.

4.8.3. Terminate Packet Detection Processing

The conductor node invokes a terminate packet detecting routine shown inFIG. 10( c) each time a terminate packet 266 is detected from any othernode. As shown, when the processing proceeds to step SP150, it isdetermined whether the terminate packet 266 is outputted from the lastnode in the transmission sequence. When the answer is “NO” here, theroutine processing is ended immediately. On the other hand, if theanswer is “YES” here, the processing proceeds to step SP152. In stepSP152, it is determined whether the shortest time period (250 msec) ofthe control cycle 240 has elapsed after start of the current controlcycle 240.

If the answer is “NO” here, the processing proceeds to step SP154 towait until the shortest time period has elapsed.

On the other hand, if the answer is “YES” here, the processing stepSP154 is skipped. Next, the processing proceeds to step SP156 in which ashort standby pause is put to the processing for the purpose ofdetecting a new node (so that the new node can inform the conductor nodeof its connection in the manner mentioned above). Then, the processingproceeds to step SP158 in which a cycle start packet 250 that reportsthe latest transmission sequence to each node is outputted, therebystarting a new control cycle 240. The transmission sequence listincluded in the cycle start packet 250 is the latest transmissionsequence list in which the change results in step SP134 of FIG. 10( a)or the change results in step SP140 of FIG. 10( b) are reflected. Then,when receiving the cycle start packet 250, each node on the network 1000holds the latest transmission sequence list included in the cycle startpacket 250.

5. Modifications

The present invention is not limited to the embodiment mentioned above,and various modifications are possible as follows:

(1) In the above-mentioned embodiment, although various kinds ofprocessing were performed by the program running on each node or theapplication program running on a personal computer, only the programsmay be stored on a recording medium like a CD-ROM or flexible disk anddistributed in the form of such a recording medium, or distributedthrough a transmission line.

(2) In the control data receiving routine (FIG. 7) executed by each nodeaccording to the above-mentioned embodiment, if any of the blocks404-410 was included in the report packet 262, the block was written instep SP48 over a corresponding portion in the node region 400-k relatedto the transmit node, and then, the CRC code was checked in step SP56.However, the sequence of both steps may be reversed. In other words, CRCcodes related to the blocks 404-410 in the report packet 262 receivedare checked, and the following processing may be such that if the CRCcode of a block is matched, the block is written over a correspondingportion, or if not matched, request data is created to request theretransmission of the block without overwriting of the block.

(3) Further, in steps SP100 to SP106 of the control data receivingroutine (FIG. 9) executed by each PC, only the change data correspondingto unconfirmed change instructions was checked as to whether the changedata contradicts the contents of the change instructions. However, inaddition to the change instructions operated on the PC, all the changedata in the RW block of any node may be error-checked, and a warning maybe generated each time an error is found. In this case, steps SP101 toSP104 may be changed as follows:

Step SP1001: In this step, it is determined whether the change data is“change data in the RO block 404.” If the answer is “NO,” the processingproceeds to step SP1002, or if the answer is “YES,” it proceeds to stepSP108.

Step SP1002: In this step, the change data are compared withcorresponding values of the RW blocks 406-410 stored on the PC todetermine whether both match with each other. If a mismatch is found,the warning processing at step SP106 is executed. If all match thecorresponding values, the processing proceeds to step SP108.

Thus, even when the processing contents are changed, unconfirmed changeinstructions on the PC can be correctly checked.

(4) In the above-mentioned embodiment, the monitoring of the settingstate or physical quantities of each amplifier I/O node, and the remotecontrol of the setting state were described by way of example toillustrate the present invention, but the monitoring and remote controlcan be performed on any other nodes, such as the general-purpose I/Onodes.

According to the first aspect of the invention, there is provided asignal transmission apparatus connected to a network as one node among aplurality of nodes involved in the network which is provided with anaudio signal transmission period for transmitting two or more channelsof audio signals (packets 211, 212, . . . , 21 n) every predeterminedtransmission cycle (200) and a control data transmission period fortransmitting control data (packet 220) using an idle time period otherthan the audio signal transmission period. The inventive apparatuscomprises a storage section (122) that stores configuration information(400) of all the nodes involved in the network, each configurationinformation (400) of each node being divided into a plurality of blocks(404-410), each block being assigned with an error-checking code (CRCcode), an error-checking code receiving section (110) that recurrentlyreceives error-checking codes of the configuration information of othernodes through the network, a comparison section that compares thereceived error-checking codes with corresponding error-checking codesstored in the storage section so as to detect a block of theconfiguration information (400) in which an error has occurred, atransmission section that transmits request data to a particular nodecorresponding to the configuration information containing the detectedblock, the request data requesting the particular node for transmissionof a block corresponding to the detected block in which an error hasoccurred, a configuration information receiving section that receivesthe corresponding block of the configuration information from theparticular node, an update section that updates the detected blockaccording to the corresponding block of the received configurationinformation, and an error-checking code updating section that creates anew error-checking code for the updated block of the configurationinformation and writes the created error-checking code into acorresponding portion of the stored configuration information.

The inventive signal transmission apparatus may further comprises anerror-checking code transmitting section (110) that recurrentlytransmits an error-checking code (CRC code) corresponding to a block ofthe configuration information which indicates its own setting state ofthe one node, and a configuration information transmitting section (110)that transmits the block of the configuration information correspondingto the error-checking code to another node when the one node receivesrequest data from said another node for requesting the transmission ofthe block of the configuration information corresponding to theerror-checking code.

As described above, according to the first aspect of the presentinvention, the signal transmission apparatus requests other nodes totransmit only the necessary block(s) according to the comparison resultsof error checking codes, so that the latest configuration information onall the nodes can be received in such an efficient manner as to minimizethe total amount of data traffic flowing through the network, therebystabilizing the data communications on the network. Further, even if theconfiguration information cannot be received from other nodes due to acommunication error, the configuration information can be made up laterin such an efficient manner as to minimize the total amount of datatraffic through the network.

According to the second aspect of the invention, there is provided asignal transmission apparatus connected, as a conductor node forcontrolling two or more nodes, to a network to which the plurality ofnodes are connected and in which an audio signal transmission period fortransmitting two or more channels of audio signals (packets 211, 212, .. . , 21 n) every predetermined transmission cycle (200) and a controldata transmission period for transmitting control data (packet 220)using an idle time period other than the audio signal transmissionperiod are provided. In the inventive apparatus, the list creationsubsection (SP134, SP140) creates a transmission order list (cycle startpacket 250) representing the order of transmission of the plurality ofnodes. The transmission section (SP158) transmits the transmission orderlist through the network. The monitoring subsection monitors whether theplurality of nodes transmit the control data according to thetransmission order list. The instruction section (SP132) detects afailed node that does not transmit the control data despite reaching itsturn transmitting the control data and instructs a node immediatelysubsequent to the failed node in the transmission sequence to transmitthe control data. When the failed node is detected, the list creationsection creates a new transmission order list from which the failed nodeis eliminated. Further comprises, the new node detection section detectswhether a new node is added to the network. When the new node isdetected, the list creation section creates a new transmission orderlist to which the new node is added.

As described above, according to the second aspect of the presentinvention, a transmission order list is transmitted to all nodespromptly in response to detection of a failed node or addition of a newnode to the network, so that all the nodes can transmit the latestconfiguration information without data collision on the network in suchan efficient manner as to minimize the total amount of data flowingthrough the network, thereby stabilizing the data communications on thenetwork.

According to the third aspect of the invention, there is provided asignal transmission apparatus connected as one of multiple nodes to anetwork in which an audio signal transmission period for transmittingtwo or more channels of audio signals (packets 211, 212, . . . , 21 n)every predetermined transmission cycle (200) and a control datatransmission period for transmitting control data (packet 220) using anidle time period other than the audio signal transmission period areprovided. IN the inventive apparatus, the storage section (122) storesconfiguration information (400) on all the multiple nodes. The receptionsection receives change instructions of configuration information on anyof the multiple nodes from a control device (PC) connected to the signaltransmission apparatus. The determination section determines whether thechange instructions are to instruct on changing configurationinformation related to the signal transmission apparatus. Theinstruction data transmitting section transmits instruction data toother nodes to make changes according to the change instructions withoutchanging the configuration information (400) on the condition that thechange instructions are to instruct on changing configurationinformation related to the other nodes. The configuration informationupdating section receives from the other nodes change data indicatingthat the configuration information has been changed at the other nodes,and changing, based on the change data, a corresponding portion(s) ofthe configuration information held in the storage section. Further, theupdate section updates a corresponding portion(s) in the storage section(122) on the condition that the change instructions are to instruct onchanging configuration information related to the signal transmissionapparatus. The change data transmitting section transmits to the othernodes change data representing the contents updated by the updatesection.

As described above, according to the third aspect of the presentinvention, a change(s) in the configuration information instructed fromthe control device can be reflected on all the nodes on the network,regardless of to which node on the network the control device isconnected, without any contradiction using a small amount of data. Eventhough control devices are connected to two or more nodes on thenetwork, respectively, each control device can change the configurationinformation independently, so that changes in the configurationinformation instructed from respective control devices can be reflectedon all the nodes on the network without any contradiction.

According to the fourth aspect of the invention, there is provided anode control method performed by a control device connected to one ofmultiple nodes connected to a network in which an audio signaltransmission period for transmitting two or more channels of audiosignals (packets 211, 212, . . . , 21 n) every predeterminedtransmission cycle (200) and a control data transmission period fortransmitting control data (packet 220) using an idle time period otherthan the audio signal transmission period are provided. The inventivemethod is carried out by a configuration information receiving step ofreceiving configuration information (400) on all the multiple nodes fromthe one node, a step of displaying the contents of the configurationinformation (400) on a display unit (136), a change operation detectingstep of detecting change operations (operations in display window 300)for instructing on changing part of the configuration information (400),a step (SP84) of notifying the one node of the change instructionscorresponding to the change operations, a step of changing or rewritingpart of the configuration information according to the changeoperations, a step of changing the display contents of the display unit(136) based on the changed configuration information, a change datareceiving step of receiving change data from the one node to inform thata portion corresponding to the change instructions has been changed, amatching determination step (SP104) of determining whether the receivedchange data matches the contents of the part of the configurationinformation, a warning step (SP106) of giving a warning of theoccurrence of a mismatch on the condition that the mismatch has beendetermined in the matching determination step (SP104), a step (SP108) ofupdating the contents of the part of the configuration information tomake them match the change data on the condition that the mismatch hasbeen determined in the matching determination step (SP104), and a step(SP108) of changing the display contents on the display unit (136) tothe contents corresponding to the change data on the condition that themismatch has been determined in the matching determination step (SP104).The node control method further comprises an operation mode setting stepof setting an operation mode for determining whether to give a warning,wherein the warning step is a step of giving a warning on the conditionthat the operation mode is set to give a warning and the mismatch hasbeen determined in the matching determination step (SP104). The nodecontrol method further comprises an indication mode changing step ofsetting, after the change operation detecting step, an indication modeof a specific portion of the display contents on the display unit (136),the specific portion instructed to change and related to theconfiguration information, in such a manner that the indication modewill be different from a normal indication mode, and an indication moderestoring step of changing the indication mode of the specific portionback to the normal indication mode after the change data receiving step.

As described above, according to the fourth aspect of the presentinvention, since the contents changed according to the operations on thecontrol device can be reflected in both the contents of theconfiguration information held in the control device and the displaycontents immediately after changing, the contents of the changeinstructions can be checked promptly on the control device. Further,when the change data related to a portion instructed to change isdifferent from the contents of the configuration information, theconfiguration information is updated according to the change data. Thismakes it possible not only to promptly check whether all the nodes onthe network are set as instructed, but also to ensure that the sameconfiguration information is held on the control device and all thenodes on the network. According to the structure in which it can beselected whether to give a warning according to the operation mode, awarning indication can be, for example, turned off on the control unitused only as a monitor to eliminate the inconvenience of viewing anerror warning over and over again and closing the error warning wheneverthe error warning is indicated. Further, according to the structure inwhich the indication mode is changed before and after the changeoperation detecting step and the change data receiving step, it ispossible to check at first sight whether the contents of changeinstructions are reflected on actually corresponding nodes and check theduration of controlling the nodes on the network (a delay in control)from the duration of indication in the different mode.

According to the fifth aspect of the invention, there is provided asignal transmission system composed of a network (1000) and two or morenodes connected to the network in which an audio signal transmissionperiod for transmitting two or more channels of audio signals (packets211, 212, . . . , 21 n) every predetermined transmission cycle (200) anda control data transmission period for transmitting control data (packet220) using an idle time period other than the audio signal transmissionperiod are provided. Each of the plurality of nodes comprises the reportsignal generating section (SP12, SP14) for generating a report signal(262) representing the state of the node every variable-length controlcycle (240), a timing detection section (118) for detecting the timingallocated to the node in each control cycle, and a transmission section(SP4, SP8, SP16, SP22) for transmitting control data (251-254) includingthe generated report signal (262) at the timing detected. A conductornode predetermined from among the plurality of nodes comprises the firstdetermination section (SP152) for determining whether a predeterminedtime period has elapsed since the start of the previous control cycle,the second determination section (SP150) for determining whether thetransmission of the control data from all the nodes is completed in thecurrent control cycle, and the cycle starting section for transmitting astart signal (cycle start packet 250) for a new control cycle (240) toall other nodes to start the new control cycle when the results of thedetermination by the first and second determination sections areaffirmative.

In the signal transmission system, the plurality of nodes include atleast first and second nodes. The first node comprises an interface(116) connected to a display unit (display unit 136 for PC) forindicating some physical quantities, and specification section (SP74)for creating instruction data specifying the physical quantities to beindicated on the display unit (PC) and measured at the second node. Thetransmission section on the first node outputs control data includingthe instruction data through the network at the timing allocated to thefirst node. The second node comprises physical quantity data creatingsection (SP20, SP22) for creating physical quantity data (264) onphysical quantities, to be measured in the second node, based on theinstruction data (physical quantities instructed from the conductor nodethrough the cycle start packet 250) included in the control datatransmitted from the first node, and the transmission section on thesecond node transmits control data including the physical quantity data(264) at the timing allocated to the second node.

In the signal transmission system, the physical quantities consist ofever-changing first physical quantities (voltage, power, impedance) andinfrequently-changing second physical quantities (temperature), and thetransmission section on the second node outputs not only physicalquantity data (264) related to the first physical quantities everycontrol cycle (240), but also physical quantity data (event data packet260) related to the second physical quantities (temperature) on thecondition that a change in any of the second physical quantities hasbeen detected.

As described above, according to the fifth aspect of the invention, inthe system for transmitting control data from all nodes through controldata transmission periods every variable-length control cycle, fasttransmission of control data can be achieved in the case of a smallamount of audio signal data. Even in the case of a large amount of audiosignal data, the duration of the control cycle can be made longer toensure the transmission of control data.

Further, according to the structure in which the second node transmitsphysical quantities instructed from the first node, the amount ofphysical quantity data transmitted on the network can be minimized. Thismakes it possible to make the occupied band on the network narrower.

Furthermore, according to the structure in which the physical quantitydata related to the infrequently-changing second physical quantities isoutputted on the condition that a change in any of the second physicalquantities has been detected, the amount of physical quantity data canbe further reduced.

1. A signal transmission apparatus connected to a network as one nodeamong a plurality of nodes which treat various physical quantities inprocessing of audio signals, the network being provided with an audiosignal transmission period for transmitting a plurality of channels ofaudio signals each transmission cycle and a control data transmissionperiod for transmitting control data of the plurality of the nodes eachcontrol cycle by using an idle time period other than the audio signaltransmission period, said signal transmission apparatus comprising: acreating section that creates instruction data which instructs anothernode to transmit a particular one of the physical quantities treated bysaid another node; a transmitting section that transmits the controldata including the created instruction data to said another node throughthe network; and a receiving section that receives the control datacontaining a value of the particular physical quantity from said anothernode.
 2. The signal transmission apparatus according to claim 1, whereinsaid one node is selected as a sole commander node among the pluralityof the nodes connected to the network for collecting the values of thevarious physical quantities treated in the plurality of the nodes.
 3. Asignal transmission apparatus connected to a network as one node among aplurality of nodes which treat various physical quantities in processingof audio signals, the network being provided with an audio signaltransmission period for transmitting a plurality of channels of audiosignals each transmission cycle and a control data transmission periodfor transmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period, said signal transmission apparatus comprising: areceiving section that receives the control data containing instructiondata form another node, the instruction data instructing said one nodeto transmit a first physical quantity and a second physical quantitytreated by said one node; and a transmitting section that transmits thecontrol data containing values of the first physical quantity and secondphysical quantity, such that the value of the first physical quantity istransmitted every control cycle, while the value of the second physicalquantity is transmitted at a control cycle immediately after a variationin the value of the second physical quantity is detected in said onenode.
 4. The signal transmission apparatus according to claim 3, whereinthe first physical quantity is variable at a high frequency as comparedto the second physical quantity, and the second physical quantity isvariable at a low frequency as compared to the first physical quantity.5. The signal transmission apparatus according to claim 3, wherein theplurality of the nodes involved in the network sequentially transmitcontrol data according to a predetermined transmission order within thecontrol data transmission period, such that said one node transmits thecontrol data at a timing when said one node comes in turn of thepredetermined transmission order.
 6. A signal transmission methodperformed in one node among a plurality of nodes c which treat variousphysical quantities in processing of audio signals, the network beingprovided with an audio signal transmission period for transmitting aplurality of channels of audio signals each transmission cycle and acontrol data transmission period for transmitting control data of theplurality of the nodes each control cycle by using an idle time periodother than the audio signal transmission period, said signaltransmission method comprising the steps of: creating instruction datawhich instructs another node to transmit a particular one of thephysical quantities treated by said another node; transmitting thecontrol data including the created instruction data to said another nodethrough the network; and receiving the control data containing a valueof the particular physical quantity from said another node.
 7. A signaltransmission method performed in one node among a plurality of nodeswhich are connected to a network and which treat various physicalquantities in processing of audio signals, the network being providedwith an audio signal transmission period for transmitting a plurality ofchannels of audio signals each transmission cycle and a control datatransmission period for transmitting control data of the plurality ofthe nodes each control cycle by using an idle time period other than theaudio signal transmission period, said signal transmission methodcomprising the steps of: receiving the control data containinginstruction data from another node, the instruction data instructingsaid one node to transmit a first physical quantity and a secondphysical quantity treated by said one node; and transmitting the controldata containing values of the first physical quantity and secondphysical quantity, such that the value of the first physical quantity istransmitted every control cycle, while the value of the second physicalquantity is transmitted at a control cycle immediately after a variationin the value of the second physical quantity is detected in said onenode.
 8. A signal transmission program executable by a computer equippedin one node among a plurality of nodes which are connected to a networkand which treat various physical quantities in processing of audiosignals, the network being provided with an audio signal transmissionperiod for transmitting a plurality of channels of audio signals eachtransmission cycle and a control data transmission period fortransmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period, said signal transmission program being executed tocause said one node to perform a method comprising the steps of:creating instruction data which instructs another node to transmit aparticular one of the physical quantities treated by said another node;transmitting the control data including the created instruction data tosaid another node through the network; and receiving the control datacontaining a value of the particular physical quantity from said anothernode.
 9. A signal transmission program executable by a computer equippedin one node among a plurality of nodes which are connected to a networkand which treat various physical quantities in processing of audiosignals, the network being provided with an audio signal transmissionperiod for transmitting a plurality of channels of audio signals eachtransmission cycle and a control data transmission period fortransmitting control data of the plurality of the nodes each controlcycle by using an idle time period other than the audio signaltransmission period, said signal transmission program being executed tocause said one node to perform a method comprising the steps of:receiving the control data containing instruction data from anothernode, the instruction data instructing said one node to transmit a firstphysical quantity and a second physical quantity treated by said onenode; and transmitting the control data containing values of the firstphysical quantity and second physical quantity, such that the value ofthe first physical quantity is transmitted every control cycle, whilethe value of the second physical quantity is transmitted at a controlcycle immediately after a variation in the value of the second physicalquantity is detected in said one node.